1) Field of the Invention
The present invention relates to chucks for gripping bits, such as standard shank drill bits. More particularly, the present invention relates to adjustable chucks for gripping bits such that the bits can be secured during a work process and released thereafter without the use of a key and without requiring two hands.
2) Description of Related Art
Chucks are used to secure a bit, or work tool, in a machine. For example, many drills, lathes, screwdrivers, and routers include chucks that can hold any of a number of different bits such as drill bits, screwdriving bits, router bits, and the like. For a rotational tool, such as a drill, the chuck must hold the bit in rotational communication with a handle or motor such that the bit is rotated as the handle or motor rotates. Additionally, many chucks also secure the bit axially so that the bit cannot be inadvertently removed from the chuck, for example, while backing a drill bit out of a workpiece. A variety of mechanisms for chucks are well known in the prior art. For example, a chuck can include a slot with a non-circular shape that corresponds to the bit. Alternatively, the slot can be keyed or include one or more set screws to secure the bit in the slot. Some chucks also use magnets to secure the bit.
In one typical chuck that is used with many drills, the chuck has a jaw assembly that can be adjusted between open and closed positions. The jaw assembly includes several jaws, usually three, that can be moved radially relative to a slot defined therebetween. The jaws are positioned in a housing that tapers toward a bit aperture for receiving the bit. As the jaws are advanced into the housing, each jaw is moved radially inward to close the slot, and the jaws can be biased with springs to open as the jaws are retracted from the housing. Typically, the jaws are axially advanced and retracted by a threaded shaft that engages the jaws through a shaft aperture of the housing opposite to the bit aperture. The threaded shaft engages the housing and can be screwed into or out of the housing using a special key.
The use of a key for securing and releasing a bit in a chuck can be time consuming and difficult, often requiring the use of two hands. Additionally, if the key is lost, the chuck can be difficult to adjust. Therefore, numerous proposals have been made for chucks that do not require a key to secure and release the bit. However, none of these proposed chucks has proven completely satisfactory, as evident by the continued use of keyed chucks.
A keyless chuck should be capable of securely holding a variety of bits, preferably including bits of different sizes. No tools should be required for opening and closing the chuck. An operator should be able to open or close the chuck and change the bit quickly, with minimal effort, and preferably with only one hand. Additionally, the chuck should be rugged to withstand harsh work environments, and cost-effective to manufacture and service.